FIG. 6 shows a floppy disk drive device (hereinafter referred to as "FDD device") as a conventional external memory device. This is a FDD device of a personal computer which is generally well known and well used. In FIG. 6, the reference numeral 7 designates a FDD device, and the reference numeral 1 designates a personal computer. In this personal computer 1, the reference numeral 2 designates a central processing unit (hereinafter referred to as "CPU"), the numeral 4 designates a standard bus thereof, the numeral 3 designates a floppy disk controller (hereinafter referred to as "FDC") which is connected to the standard bus 4. The reference numeral 5 designates an operating system (hereinafter referred to as "OS") which is a standard software system for operating the personal computer 1. Besides, the memory section, the display control section, and the key control section are not illustrated for simplification.
FIG. 8 shows a construction of an OS called CP/M which is commonly used in a personal computer as the above-described OS 5. In FIG. 8, the basic constitution of the software of CP/M comprises a console command processor (CCP) 16, a basic disk operating system (BDOS) 17, and a basic input/output (I/O) system (BIOS) 18.
FIG. 7 shows a basic construction of the FDD device. In FIG. 7, the reference numeral 12 designates a reading out magnetic head, the numeral 8 designates a reading out control section for controlling the reading out magnetic head 12. The reference numeral 13 designates a writing in magnetic head, and the reference numeral 9 designates a writing in control section for controlling the writing in magnetic head 13. The reference numeral 11 designates a mechanism section, and the reference numeral 10 designates a mechanism control section for controlling the mechanism section 11. The reference numeral 14 designates a floppy disk. These portions are controlled through the FDD I/O bus 6.
FIG. 9 shows a prior art semiconductor disk device 20 which is connected to the personal computer 1 as an external recording material. As shown in FIG. 9, the conventional semiconductor disk device 20 comprises a bus conversion circuit 21, a memory circuit 22, and a battery 23. The reference numeral 19 designates an I/O bus, and this is controlled under the above-described BIOS 18 in the personal computer 1.
The operation of the external storing system in the prior art FDD device will be described. This system is commonly used in a terminal such as a personal computer, and its operation is reported in an operation manual or an article. Only the summary thereof will be described.
The recording format of the floppy disk 14 is standardized as IBM format, and those which are IBM formated are used for the floppy disks 14. In the IBM format, the size of the disk, the track number/side, and the sector format are defined, and the floppy disks in accordance with these definitions have the compatibility. Generally, as means for controlling the floppy disk 14, a FDC 3 is provided which conducts a control in accordance with the IBM format through the standard bus 4 of the personal computer 1 as shown in FIG. 6. This FDC 3 conducts an interface processing with the CPU 2 as well as conducts the reading out and writing in of the floppy disk 14 in the FDD device 7 through the FDD I/O bus 6.
The floppy disk 14 has generally a configuration of a standard 45-rpm record, and this is produced by plating magnetic material on mica, and information is magnetically recorded therein. When the power supply of the FDD device 7 is applied, the mechanism control section 10 and the mechanism section 11 operate, and the floppy disk position 14 is automatically determined and is rotated at a predetermined speed. The reading out from and writing in into this floppy disk 14 of information is conducted by the reading out head 12 and the writing in head 13, respectively. These heads are generally provided on a carriage connected to a stepping motor provided at the mechanism portion 11, and these heads are produced of stainless copper. The reading out and writing in of the information at a desired track position and sector position are conducted by moving the heads 12 and 13 on a circular plate in a direction towards the center of the floppy disk or in the reverse direction. The control of the movements of these heads 12 and 13 is conducted by operating the stepping motor of the mechanism section 11 in accordance with the track number from the signal output on the FDD I/O bus 6. The signal from the reading out head 12 is amplified by the reading out control section 8 before being outputted because the initial signal is weak.
The operation of the CP/M OS 5 will be described with reference to FIG. 8. The CCP 16 and the BDOS 17 are fixed sections which do not change in accordance with the user, and the BIOS 18 is a section which depends on the physical hardware interface of the system and varies as the system varies. Usually the CCP 16 processes a command from the key board, and the BDOS 17 processes a file of the disk. The BIOS 18 has an I/O subroutine such as key processing, display processing, print out processing, or disk I/O processing linked to the OS 5, and even when a FDD device is connected as an external memory device, the BIOS 18 is completely file-controlled under the OS 5.
Next, the operation in a case where a semiconductor disk device shown in FIG. 9 is used as an external memory device will be described.
In this case a semiconductor disk 20; comprising a bus conversion circuit 21, a memory circuit 22, and a battery 23; is connected to the I/O bus 19 which is a hardware interface supported by the BIOS 18, and the bus conversion circuit 21 is provided between the I/O bus 19 and the memory circuit 22 because the I/O bus 19 controlled by the BIOS 18 and the bus of the memory circuit 22 generally have different structures. The information of the memory circuit 22 is stored with the use of the battery 23. This semiconductor disk device 20 conducts the similar operation as that of the above-described FDD device because the disk device 20 is controlled by the BIOS 18, and it is also made possible to transfer information freely between the FDD device 7 and the semiconductor disk device 20 in consequence of the file-controlling function of the BDOS 17. The difference between the semiconductor disk device and the FDD device 7 is that the semiconductor disk can conduct an electrical high speed information processing.
The following are disadvantages in the prior art FDD device.
(1) Its mechanical structure creates a restriction in the endurance of the rotating portion and the head portion at a continuous operation. PA1 (2) The presssing of the head against the magnetic surface reduces the life-time of the floppy disk. PA1 (3) The floppy disk has a size of 5 to 8 inches diameters requiring a large space for their storage. Furthermore, when the handling or carrying of the floppy disk, one must safeguard from temperature extremes and the folding or the curving of the disk, to protect the magnetic surface. PA1 (4) The operation speed is quite low because the reading out and writing in is conducted mechanically and magnetically. PA1 (5) The data error ratio is large compared to the semiconductor memory. PA1 (1) The memory circuit is large in size, fixed, and not portable. PA1 (2) A partial default of the memory circuit may possibly become a fatal wound. PA1 (3) The utility value of information such as an application software stored in the memory circuit is low. PA1 (4) The contents of all the memory circuits will vanish due to a battery fault. PA1 (5) It is difficult to change the memory element or to enlarge the memory capacity of the device, and therefore, the maintenance and inspection are complicated.
Although the above-described disadvantages of the FDD device are improved by using a semiconductor disk, the prior art semiconductor disk has the following drawbacks.
The conventional FDD device and semiconductor disk device have the above-described disadvantages.